Hologram and its holographic process

ABSTRACT

The invention relates to a security-conscious hologram which can apply a sufficient three-dimensional appearance to a reconstructed image in both its vertical and horizontal directions, and which is difficult to illegally copy and easily told from any illegal copy forged from it, and a holographic process of recording it The hologram H 2  is of a combined reflection and volume type, wherein a subject image P is recorded, and minute reflection images F and O′ from a light source are recorded at least in front of, or in the rear of, the subject image P, both in a reconstructible fashion, and a viewing position E is moved along a hologram surface, so that the subject image P and the minute reflection images F and O′ are viewable at varied relative positions.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 11/483,562 filed Jul. 11,2006. The entire disclosure of the application Ser. No. 11/483,562 ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally to a hologram and itsholographic process, and more particularly to a security-conscioushologram that is much less vulnerable to illegal copying and can beeasily told from any illegal copy forged from it, and a holographicprocess for the same.

Holograms, thanks to their aesthetic attributes, have been on the marketalso for prevention of illegal copying by visual authentication.Holograms appearing on the market, for the most part, have been of theembossed type fabricated with a variety of designs capable of visualauthentication. However, such embossed holograms are now easier tofabricate, on the way out for prevention of illegal copying.

In this conjunction, the embossed type hologram has been a sort ofexpression wherein a certain direction parallax alone is intervened, andso a three-dimensional appearance is obtained in that direction alone.As a hologram comparable to the embossed type hologram, a volumehologram has been developed, foraying into the illegal copyingpreventive field. For the volume hologram capable of applying athree-dimensional appearance to the reconstructed image irrespective ofvertical and horizontal directions, authentication is required by makinga design difference with a conventional embossed hologram. When anordinary model is holographically recorded in the volume hologram, it ispossible to apply a three-dimensional appearance to the length directionas well as to the width direction. With some volume holograms, however,a reconstructed image cannot be easily in sight depending on object'ssolidity, light source, and design.

So far, a volume hologram for prevention of illegal copying withordinarily invisible fine patterns three-dimensionally recorded in ithas been known from Patent Publication 1 as an example. Even with this,however, it would be not easy to ensure such a sufficientthree-dimensional appearance as mentioned above.

Patent Publication 1: JP-A 11-24538

SUMMARY OF THE INVENTION

Such being the prior art, the present invention has for its object theprovision of a security-conscious hologram which ensures to apply asufficient three-dimensional appearance to an reconstructed image inboth its vertical and horizontal directions, and which is difficult toillegally copy and easily told from any illegal copy forged from it, andits holographic process.

According to the present invention, this object is achievable by theprovision of a hologram comprising a hologram of a reflection and volumetype, characterized in that a subject image is recorded, and a minutereflection image of a light source is recorded at least in front of, orin the rear of, said subject image, both in a reconstructible fashion,and a viewing position is moved along a hologram surface whereby saidsubject image and said minute reflection image are viewed at variedrelative positions.

In a preferable embodiment of the invention, said subject imagecomprises a partially distorted image. For instance, said subject imagemay comprise a character pattern, a part of which may comprise adistorted character pattern portion. In this case, said distortedcharacter pattern portion of said subject image and otherdistortion-free character pattern portion are in inverse contrast.

In one embodiment of the invention, minute reflection images may berecorded both in front of and in the rear of said subject image in areconstructible fashion, and said front minute reflection image and saidrear minute reflection image may be reflection images with respect tothe same light source.

In another preferable embodiment of the invention, minute reflectionimages may be recorded both in front of and in the rear of said subjectimage in a reconstructible fashion, and the amount of a change in therelative position of at least one of the minute reflection images withrespect to the said subject image is greater than ½ of the diameter ofsaid subject image.

The present invention also provides a holographic process of recording ahologram, characterized in that a refractive index object is located ona hologram recording side of a subject, and first object light comingout said subject through said refractive index object and second objectlight comprising at least one of light reflected at an incidence sidesurface of said refractive index object upon illumination of saidrefractive index object with illumination light from the hologramrecording side and light reflected at an output side surface of saidrefractive index object upon refraction at the incidence side surface ofsaid refractive index object are entered in a hologram recordingmaterial located on the hologram recording side of said subject while,at the same time, reference light is entered in said hologram recordingmaterial, for interference and hologram recording.

Further, the present invention provides a holographic process ofrecording a hologram, characterized in that a semi-transmittingreflective surface is located on a hologram recording side of a subject,and first object light coming out of said subject through saidsemi-transmitting reflective surface and second object light reflectedat said semi-transmitting reflective surface upon illumination of saidsemi-transmitting reflective surface with illumination light from thehologram recording side are entered in a hologram recording materiallocated on the hologram recording side of said subject while, at thesame time, reference light is entered in said hologram recordingmaterial, for interference and hologram recording.

In the above two holographic processes, said illumination light to bedirected from the hologram recording side to said refractive indexobject or said semi-transmitting reflective surface may be directedthereto from the front of said hologram recording material upontransmitting through said hologram recording material.

Preferably in that case, said illumination light to be directed to saidrefractive index object or said semi transmitting reflective surfaceconverges near a position at which said illumination light transmitsthrough said hologram recording material.

It is also preferable that at least one of the incidence side surfaceand output side surface of said refractive index object comprises acurved or bent surface other than a plane.

Preferably in that case, said refractive index object comprises apiano-convex positive lens having a convex surface on its incidence sideand a plane surface on its output side, which, for hologram recording,is located in such a way as to satisfy at least one of the followingconditions (1) and (2):

tan⁻¹ {(H−2R)/4L}≦θ ₁≦tan⁻¹ {(2H−R)/2L}  (1)

tan⁻¹ {(H+2R)/4L}≦θ ₂≦tan⁻¹ {(2H+R)/2L}  (2)

where θ₁ is the angle of incidence on said hologram recording materialof light occurring from reflection of illumination light at the outerperipheral end of the incidence side convex surface of said piano-convexpositive lens, θ₂ is the angle of incidence on said hologram recordingmaterial of light occurring from refraction of illumination light at theentrance convex surface of said piano-convex positive lens andreflection of illumination light at the outer peripheral end of theoutput side plane of the piano-convex positive lens, L is the distancefrom said hologram recording material to the subject, H is the size ofsaid hologram recording material, and R is the diameter of saidplano-convex positive lens.

It is also preferable that said semi-transmitting reflective surfacecomprises any of a plane, a curved surface, a bent surface or a discretesurface.

According to the holographic process of the invention, said referencelight is entered in the hologram recording material from the same sidefor said first object light and said second object light to record thefirst hologram therein, and reconstructing illumination light is enteredin said first hologram to generate diffracted light while, at the sametime, another reference light is entered in a volume hologram recordingmaterial located at a position of incidence of said diffracted light forinterference, thereby recording the second hologram therein. In thisway, the hologram of the invention is obtainable.

The present invention also encompasses a hologram recorded by theforegoing holographic processes.

In the hologram of the invention, a subject image is recorded, and aminute reflection image of a light source is recorded at least in frontof, or in the rear of, said subject image, both in a reconstructiblefashion, and a viewing position is moved along a hologram surfacewhereby said subject image and said minute reflection image are viewedat varied relative positions. The three-dimensional appearance of thesubject image including the degree of transformation is combined withthe relative position, direction of movement, and number of the minutereflection image simultaneously recorded in the hologram, making illegalcopying much more difficult and determination of whether that hologramis genuine or an illegal copy much easier.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts, which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical path representation illustrative of one example ofthe first step of the holographic process according to the invention.

FIG. 2 is illustrative of an object image that occurs upon irradiationwith the first object illumination light and the second objectillumination light.

FIG. 3 is illustrative of an arrangement for recording a reflectionhologram at the second step.

FIG. 4 is illustrative of an image reconstructed from the secondhologram.

FIG. 5 is illustrative of an exemplary character pattern, itsmodifications, and its transformed images.

FIG. 6 is a representation of the angle range for the outermost lightray of reflected light that, when the first hologram corresponding toFIG. 1 is holographically recorded, propagates in such a way as todiverge from the point of divergence O′.

FIG. 7 is a representation of the angle range for the outermost lightray of reflected light that, when the first hologram corresponding toFIG. 1 is holographically recorded, propagates in such a way as todiverge from the point of divergence F.

FIG. 8 is illustrative of exemplary refractive index 20 bodies locatedin front of a subject.

FIG. 9 is illustrative of exemplary semi-transparent mirrors located infront of the subject.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The holograms and holographic processes of the present invention are nowexplained with reference to the accompanying drawings.

First of all, the hologram of the invention is explained in order ofholographic process steps. The hologram of the invention isholographically recorded at two steps.

FIG. 1 is an optical path representation illustrative of one example ofthe first step of the holographic process according to the invention. Aplanar transmission type subject 2 is located facing one side (the rightside of FIG. 1) of a first hologram recording material 1 such as aphotopolymer. An example of the subject 2 will be described later. Andthen, a lens 3 is located on the side of the subject 2 facing therecording material 1. The lens 3 here is a piano-convex positive lenswith its planar side located in contact with, or slightly spaced awayfrom, the subject 2. A diffuser 4 is positioned in contact with the sideof the subject 2 that faces away from the lens 3. Then, as thetransmission type subject 2 is illuminated with object illuminationlight 5 from the side of this diffuser 4, diffused light transmittingthrough the transmission type subject 2 goes through the lens 3 locatedin front of it, forming a virtual image of the subject 2. Then, firstobject light 11 propagating as if it came out of that virtual image isincident on one side of the first hologram recording material 1.

On the other hand, a mask 6 having a minute aperture 7 is located facingthe other side (the left side of FIG. 1) of the first hologram material1. As the second object illumination light 9 is directed to the maskthrough a positive lens 10 substantially from the front facing away fromthe recording material 1, light 8 transmitting through the aperture 7 inthe mask 6 once converges, transmitting through the recording material 1located near its point of convergence and incident, as divergent lightthis time, on the lens 3, where a part of the illumination lightreflects (Fresnel reflection) off the convex front surface and planarback surface, becoming the second object light 12 to be incident on oneside of the first hologram recording material 1.

Here, reference light 13 is obliquely entered, simultaneously with thefirst object light 11 and the second object light 12, in the firsthologram recording material 1 from the same side as the incidence sidefor the first object light 11 and the second object light 12 forinterference. Finally, a first hologram H1 is recorded by development inthe first hologram recording material 1.

An image recorded in the hologram H1 in such an arrangement is nowexplained. FIG. 2 is illustrative of an object image that occurs uponsuch illumination by the first object light 5 and the second objectlight 9 as described above. The diffused light transmitting through theplanar transmission type subject 2 passes through the lens 3 to form avirtual image P of the subject 2, which image is in a convex shape asviewed from the side of the recording material 1. The first object light11 of FIG. 1 enters the first hologram recording material 1 just aslight coming out of this virtual image P.

Meanwhile, the light 8, which transmits through the aperture 7 in themask 6, once converges and then diverges, is incident on the convexsurface 31 of the lens 3 on the side of the recording material 1, wherea part of that light is subjected to Fresnel reflection. The resultingreflected light 12 ₁ enters the first hologram recording material 1 justas light diverging from a point O′ in the rear of the convex surface 31.

Further, the portion of the light 8 transmitting through the convexsurface 31 of the lens 3 is refracted at that surface 31, traveling insuch a way as to converge on another point F′ behind the convex surface31 Then, the light is incident on the plane 32 of the lens 3 on the sideof the subject 2, traveling toward a point F that is an image of thepoint F′ and on the side of the lens 3 facing the recording material 1,and arriving at that point F, after which it enters the first hologrammaterial 1 as light 12 ₂ diverging from the point F.

The reflected light 12 ₁ traveling in such a way as to diverge from thepoint O′ and the reflected light 12 ₂ diverging from the point F mergetogether into the second object light 12, which then enters the firsthologram recording layer 1.

As can be seen from the foregoing explanation, the object imageholographically recorded in the hologram H1 by interference with thereference light 13 comprises the virtual image P of the subject 2 by thelens 3 (FIG. 2), the point of divergence O′ behind it and the point ofdivergence F in front of it.

The first hologram H1 recorded in the first hologram recording material1 as mentioned above is then used to record a reflection hologram H2 atthe second step, A specific arrangement to this end is shown in FIG. 3.The first hologram H1(1) holographically recorded in the arrangement ofFIG. 1 is located at the position of FIG. 1, and reconstructingillumination light 22 traveling oppositely to the reference light 13 forholographic recording is entered in the first hologram H1(1) from theside that faces away from the incidence side for the reference light 13for back surface recording. Thereupon, forwardly diffracted light 23yields reconstruction real images of the virtual image P of the subject2, the point of convergence F defined by refraction at the front convexsurface 31 of the lens 3 and reflection at the back plane 32 thereof andthe point of divergence O′ defined by reflection at the convex surface31 (such reconstruction images, too, are shown by the same P, F, O′) arereconstructed while the spatial arrangement for recording is keptintact. A second hologram recording material 21 comprising a volumehologram recording material such as a photopolymer is placed near suchreconstructed images (near the virtual image P of the subject 2 in FIG.3), and reference light 24 is simultaneously entered in the secondhologram recording material 21 this time from the side that faces awayfrom the incidence side for the diffracted light 23 for interference anddevelopment, thereby recording the second hologram H2 in the secondhologram recording material 21. This second hologram H2 becomes thesecurity-conscious hologram of the invention. Alternatively, theinventive security-conscious hologram having similar properties may alsobe obtained by holographic replication of the second hologram H2. Notehere that this hologram is a reflection hologram.

FIG. 4 is illustrative of an image reconstructed from the thus obtainedsecond hologram H2. As reconstructing illumination light 25 travelingoppositely to the reference light 24 for holographic recording isentered in the second hologram H2(21) from the side that faces away fromthe incidence side for the reference light 24, a transformed image P ofthe subject 2 by the lens 3, the point F defined by refraction at thefront surface 31 of the lens 3 and reflection at the back surface 32 andthe point O′ defined by refraction at the front surface 31 of the lens 3are reconstructed as real or virtual images (the image P and the point Freconstructed as real images and the point O′ as a virtual image in FIG.4), while the spatial arrangement for holographic recording is keptintact. Therefore, as the eye E of the viewer is positioned on theincidence side of the reconstructing illumination light 25, it allowsthe viewer to view the transformed image P, the point F and the point O′while the stereoscopic arrangement for holographic recording ismaintained. To an ordinary viewer, however, the points F and O′ areunnoticeable or appear to be only a reflection of the surrounding lightsource image; in any event, they are not that obtrusive.

On the other hand, consider now that the transmission type subject 2 issuch a character pattern as shown in FIG. 5( a). With the lens 3 ofpositive power placed on that, even when the transformed image P is seenas a plane image, there is a character pattern which, as depicted inFIG. 5( b), is distorted at only a site with the lens 3 placed on it,making the image P convex toward the eye E side, and thereby applying asufficient three-dimensional appearance to the image P in both verticaland horizontal directions.

And then, these images F, P and O′ are reconstructed in the orderdepicted in FIG. 4 while they are lined up in the depth direction.Consider now the intermediate transformed image P of the subject 2 as areference. the viewer moves his eye E relatively up (indicated by an“up” arrow in FIG. 4), it causes the image F to move down and the imageO′ to move up. Conversely, as the viewer moves his eye E relatively down(indicated by a “down” arrow in FIG. 4), it allows the image F to moveup and the image O′ to move down.

Thus, given the three-dimensional appearance of the subject image Pincluding the degree of transformation of the character pattern and therelative positions and relative movement directions of the images F andO′ simultaneously recorded in the hologram, whether that hologram is agenuine one or an illegal copy can be easily determined.

Next, consider the range wherein the images O′ and F are seen when theviewer moves his eye E relatively to the second hologram H2, and therange of movement of the images O′ and F with respect to the transformedimage P.

FIG. 6 is a representation of the angle range for the outermost lightray 12 ₁₀ of light 12 ₁ reflected at the convex surface 31 of the lens3, which travels in such a way as to diverge out of the point ofdivergence O′ in the holographic process of the first hologram H1corresponding to FIG. 1. Primarily by setting the radius of curvature ofthe convex surface 31, the minimum θ_(1min) to the maximum θ_(1max)incidence angle range with respect to the first hologram recordingmaterial 1 is determined. Here, let L be the distance from the firsthologram recording material 1 to the subject 2, H be the size of thefirst hologram recording material 1, R be the diameter of the lens 3,and θ₁ be the angle of incidence on the first hologram recordingmaterial 1 of the light 12 ₁₀ reflected at the outer peripheral end ofthe convex surface 31 of the lens 3. Then, there are

θ_(1min)=tan⁻¹ {(H−2R)/4L}

θ_(1max)=tan⁻¹ {(2H−R)/2L}

The angle of incidence on the first hologram recording material 1 of thelight 12 ₁₀ reflected at the outer peripheral end of the convex surface31 of the lens 3 is set at θ₁ in such a way as to satisfyθ_(1min)≦θ_(1≦θ) _(1max), that is,

tan⁻¹ {(H−2R)/4L}≦θ ₁≦tan⁻¹ {(2H−R)/2L}  (1)

so that the visibility of the movement of the image O′ in the finallyobtained second hologram H2 can be gained.

That is, the lower limit θ_(1min) to θ₁ implies that when the viewermoves his eye E relatively up or down, as depicted in FIG. 4, the rangewherein the image O′ that moves with respect to the transformed image Pof the subject 2 in the same direction can be viewed is limited to therange of ±H/4 from the center of the original first hologram H1(1); asthe limits ±H/4 are reached, the image O′ arrives at the outer peripheryof the transformed image P; and as the viewer moves his eye E beyondthose limits, the image O′ is no longer in sight. Likewise, the upperθ_(1max) to θ₁ implies that when the viewer moves his eye E up or downto the outer periphery of the original first hologram H1(1), the imageO′ reaches a position of nearly ½ from the center of the transformedimage P; and as the viewer moves his eye E beyond the outer periphery ofthe original first hologram H1(1), the image O′ is no longer in sightbecause the reflected light 121 is not recorded in the second hologramH2.

Thus, when θ₁ is near the lower limit of θ_(1min)≦θ_(1≦θ) _(1max), theimage O′ is allowed to move within the range of the transformed image P;however, the range wherein the viewer can move his eye E to view theimage O′ is limited to about ±H/4 from the center of the original firsthologram H1(1). Likewise, at near the upper limit, the range wherein theviewer can move his eye E to view the image O′ comes within the range ofthe original first hologram H1(1); however, the range of relativemovement of the image O′ is limited to within the range of about ½ ofthe diameter of the transformed image P from its center, where the speedof relative movement is slow.

And of course, if θ₁ satisfies

θ₁=tan⁻¹ {(H−R)/2L}

so that the reflected light 12 ₁₀ can be incident on the outer peripheryend of the first hologram recording material 1, then the image O′ canmove relatively within the range of the transformed image P and therange wherein the viewer can move his eye E to view the image O′ comeswithin the range of the original first hologram H1(1), where there isthe highest visibility obtained.

FIG. 7 is a representation of the angle range for the outermost lightray 12 ₂₀ of light 12 ₂ reflected at the convex surface 31 of the lens 3upon refraction through the convex surface 31 of the lens 3, whichtravels in such a way as to diverge out of the point of divergence F inthe holographic process of the first hologram H1 corresponding toFIG. 1. Primarily by setting the radius of curvature of the convexsurface 31 and the refractive index of the lens 3, the minimum θ_(2min)to the maximum θ_(2max) incidence angle range with respect to the firsthologram recording material 1 is determined. L, H and R here have thesame definitions as given with reference to FIG. 6, and θ₂ is the angleof incidence on the first hologram recording material 1 of the light 12₂₀ reflected at the outer periphery end of the plane 32 of the lens 3.Then, there are

θ_(2min)=tan⁻¹ {(H+2R)/4L}

θ_(2max)=tan⁻¹ {(2H+R)/2L}

The angle of incidence on the first hologram recording material 1 of thelight 12 ₂ reflected at the outer peripheral end of the convex surface31 of the lens 3 is set at θ₂ in such a way as to satisfyθ_(2min)≦θ_(2≦θ) _(2max), that is,

tan⁻¹ {(H+2R)/4L}≦θ ₂≦tan⁻¹ {(2H+R)/2L}  (2)

so that the visibility of movement of the image F in the finallyobtained second hologram H2 can be gained. That is, as is the case withFIG. 6, the lower limit θ_(2min) to θ₂ implies that when the viewermoves his eye E relatively up or down, as depicted in FIG. 4, the rangewherein the image F that moves with respect to the transformed image Pof the subject 2 in the opposite direction can be viewed is limited tothe range of ±H/4 from the center of the original first hologram H1(1);as the limits ±H/4 are reached, the image F arrives at the outerperiphery of the transformed image P; and as the viewer moves his eye Ebeyond those limits, the image F is no longer in sight. Likewise, theupper θ_(2max) to θ₂ implies that when the viewer moves his eye E up ordown to the outer periphery of the original first hologram H1(1), theimage F reaches a position of nearly ½ from the center of thetransformed image P; and as the viewer moves his eye E beyond the outerperiphery of the original first hologram H1(1), the. image F is nolonger in sight because the reflected light 12 ₂ is not recorded in thesecond hologram H2.

Thus, when θ₂ is near the lower limit of θ_(2min)≦θ_(2≦θ) _(2max), theimage F is allowed to move within the range of the transformed image P;however, the range wherein the viewer can move his eye E to view theimage F is limited to about ±H/4 from the center of the original firsthologram H1(1). Likewise, at near the upper limit, the range wherein theviewer can move his eye E to view the image F comes within the range ofthe original first hologram H1(1); however, the range of relativemovement of the image F is limited to within the range of about ½ of thediameter of the transformed image P from its center, where the speed ofrelative movement is slow.

And of course, if θ₂ satisfies

θ₂=tan⁻¹ {(H+R)/2L}

so that the reflected light 12 ₂₀ can be incident on the outer peripheryend of the first hologram recording material 1, then the image F canmove relatively within the range of the transformed image P and therange wherein the viewer can move his eye E to view the image O′ comeswithin the range of the original first hologram H1(1), where there isthe highest visibility obtained.

Incidentally, it is understood that because the hologram H2 of theinvention is of the combined volume and reflection type, it can indeedbe fully reconstructed and viewed with white light in ordinaryenvironments without recourse to such reconstructing illumination light25 as shown in FIG. 4.

By the way, when the transmission type subject 2 is such a characterpattern as shown typically in FIG. 5( a), it is preferable to previouslyapply such distortion as depicted in FIG. 5( b) to that transmissiontype subject 2, thereby giving a lot more enhancement to the degree oftransformation of the transformed image P. This is because, in thetransformed image P with distortion applied to it through the lens 3,the distortion of the portion of the image with the lens 3 placed on itis more enhanced, making the image P more convex toward the eye E sideand, hence, applying a lot more striking three-dimensional appearance toit in both the vertical and horizontal directions.

Just as the subject 2 corresponding to FIG. 5( b) and illustrated inFIG. 5( d), the character pattern for the subject 2 may comprise apositive image deformable by the lens 3 and a negative image of oppositecontrast with the lens 3 not placed on it. In the transformed image Pwith distortion applied to it through the lens 3, the contrast of theportion with the lens 3 placed on it is so reversed that a lot moreexpression can be added to the reconstructed image. In FIG. 5( d),distortion is much more enhanced and, hence, illegal copying grows moredifficult.

For the transparent body which, in the holographic process of recordingthe first hologram H1, is located on the side of the subject 2 facingthe recording material 1 to transform the image of the subject, variousrefractive index bodies may be used, to say nothing of the plano-concavelens (lens 3 in FIG. 1) as shown in FIG. 8( a). Specific examples areshown in FIGS. 8( b)-8(f). FIG. 8( b) shows a double-convex lens ofpositive power; FIG. 8( c) shows a piano-concave lens of negative power;and FIG. 8( d) shows a double-concave lens of negative power. Use mayalso be made of a refractive index object which, as shown in FIG. 8( e),has any arbitrary curved surface or surfaces (of wave shape in FIG. 8(e)) on one side or both sides or, as shown in FIG. 8( f), has a bentsurface or surfaces (of toothed bent shape in FIG. 8( f)) on one side orboth sides. These are mentioned by way of example alone but not by wayof limitation.

Thus, by holographically recording the hologram of the invention whilevarious such refractive index bodies are located in front of the subject2, a lot more transformation can be added to the subject image P and alot more three-dimensional appearance can be added to the reconstructedimage, making illegal copying much more difficult. In addition, thereare a lot more variations in the relative position, direction ofmovement and number of images corresponding to the images F and O′simultaneously recorded in the hologram, which make illegal copying muchmore difficult, and make determination of whether that hologram is agenuine one or an illegal copy much easier.

For the transparent body which, in the holographic process of recordingthe first hologram H1, is located on the subject 2 facing the recordingmaterial 1, semitransparent mirrors of various surface shapes(semi-transmitting reflective surfaces) may be used, to say nothing ofsuch a refractive index object having partially reflective front andrear surfaces as shown in FIG. 8. Note here that each is located awayfrom the subject 2. With such a semi-transparent mirror, there is notransformation of the subject image; however, there are a lot morevariations in the relative position, direction of movement, and numberof images corresponding to the images F and O′ simultaneously recordedin the hologram, which make illegal copying much more difficult, andmake determination of whether that hologram is a genuine one or anillegal copy much easier. Exemplary such semi-transparent mirrors areshown in FIG. 9( a) to FIG. 9( e). FIG. 9( a) shows that a simple planesemi-transparent mirror is located parallel with the subject 2; FIG. 9(b) shows that a convex semi-transparent mirror of negative power islocated in front of the subject 2; FIG. 9( c) shows that a planesemi-transparent mirror is located obliquely to the subject 2; FIG. 9(d) shows that a semitransparent mirror having any arbitrary curvedsurface (of wave shape here) is located in front of the subject 2; andFIG. 9( e) shows that a semi-transparent mirror having discrete,partially reflective regions is located in front of the subject 2. Thesemirrors placed in front of the subject 2 are mentioned by way of examplealone but not by way of limitation. Note here that the proportion of thereflectivity and transmittance of each semi-transparent mirror(semi-transmitting reflective surface) may be determined as desired.

While the hologram of the invention and the holographic process ofrecording it have been explained with reference to some specificembodiments, it is understood that the invention is never limited tothem, and so many modifications could be possible.

1. A hologram of a combined reflection and volume type, characterized inthat a subject image is recorded, and a minute reflection image of alight source is recorded at least in front of, or in the rear of, saidsubject image, both in a reconstructible fashion, and a viewing positionis moved along a hologram surface whereby said subject image and saidminute reflection image are viewed at varied relative positions.
 2. Thehologram according to claim 1, characterized in that said subject imagecomprises a partially distorted image.
 3. The hologram according toclaim 2, characterized in that said subject image comprises a characterpattern, a part of which may comprise a distorted character patternportion.
 4. The hologram according to claim 3, characterized in thatsaid distorted character pattern portion of said subject image and otherdistortion-free character pattern portion are in inverse contrast. 5.The hologram according to any one of claims 1-4, characterized in thatsaid minute reflection images are recorded both in front of and in therear of said subject image in a reconstructible fashion, and said frontminute reflection image and said rear minute reflection image arereflection images with respect to the same light source.
 6. The hologramaccording to claim 5, characterized in that said minute reflectionimages are recorded both in front of and in the rear of said subjectimage in a reconstructible fashion, and an amount of a relative positionchange of at least one of the minute reflection images with respect tothe said subject image is greater than ½ of the diameter of said subjectimage.